package javaIO;

import java.io.File;
import java.io.FilenameFilter;
import java.util.regex.Pattern;

public class DirList {
    public static void main(String[] args){
        File path = new File(".");
        String[] list;
        if (args.length == 0){
            list = path.list();
        }
        else
        {
            list = path.list(new DirFilter(args[0]));
        }
        for (String dirItem : list){
            System.out.println(dirItem);
        }
    }
}

class DirFilter implements FilenameFilter{
    private Pattern pattern;
    public DirFilter(String regex){
        pattern = Pattern.compile(regex);
    }
    @Override
    public boolean accept(File dir, String name) {
        return pattern.matcher(name).matches();
    }
}
